Fan Assembly With Fan Blade Under-Root Spacer

ABSTRACT

A fan assembly is disclosed which includes a rotor having an outer periphery and at least one slot extending radially inwardly through the outer periphery. The slot terminates at a base surface disposed at a radial depth from the outer periphery of the rotor. The fan assembly also includes at least one fan blade that includes an airfoil connected to a root. The root is received in the slot. The root terminates in an inner face having a radial length that is less than the radial depth of the Slot to define a gap between the inner face of the root and the base surface of the slot when the root is bias away to the base surface of the slot. A spacer is disposed within a gap, wherein a spacer is fabricated from a polymer, which may be a composite material such as a polymer embedded with reinforcing materials such as carbon fibers and glass fibers.

CROSS-REFERENCE TO RELATED APPLICATION

This Application is a non-provisional patent application claimingpriority under 35 CSC §119(e) to U.S. Provisional Patent ApplicationSer. No. 61/924,892 filed on Jan. 8, 2014.

BACKGROUND

1. Technical Field

This disclosure relates to turbomachinery and, more particularly, tovarious means for holding a turbomachinery fan blade in a radially tightfashion within a supporting rotor slot.

2. Description of the Related Art

Turbomachinery fan blades may be secured to a supporting rotor byproviding shaped slots in the rotor that mateably receivecorrespondingly shaped roots of the fan blades. For example, the rotorsmay include dovetail or fir tree shaped slots that receivecorrespondingly shaped roots disposed at the radially inwardly ends ofthe fan blades. The slots of the rotor and the roots of the fan bladesare adapted to lock the fan blades against radial movement as the rotorspins about its axis.

However, for large fan blades, such as high bypass ratio fan blades,interlocking blade shrouds may also be used to prevent excessive bladedeflection and to dampen vibration. The combination of interlockingblade shrouds and a root/slot locking system for the fan blades androtor can make it difficult or impossible to insert the fan blades inthe slots of the rotor and/or to remove the fans blades from the rotorfor service and/or replacement purposes. To facilitate removal andreplacement of a shrouded and locked fan blade from a fully assembledrotor, the slots may be oversized so that a fan blade may be movedradially inwardly a sufficient distance to permit the distal tip of thefan blade to clear the interlocking blade shrouds.

Where such radially oversized slots are utilized, spacers may be used tohold each blade radially tight within its respective slot. Such spacersmay also facilitate balancing of the rotor and may prevent hammeringand/or relative motion between abutting blade root and rotor surfaces,which may increase wear and therefore increase maintenance costs.

Typically, such spacers may be formed from a metallic material, whichmay cause galling during operation as the fan blade root and the rotorslot engage the metallic spacer. Further, metallic spacers may causedamage to the fan blade roots and/or the rotor slots during installationor removal of the fan blades from the rotor. Moreover, metallic spacersmay be suitable for use only in closely toleranced rotor slots, therebylimiting their applicability.

SUMMARY OF THE DISCLOSURE

In one aspect, a fan assembly for turbomachinery is disclosed. Thedisclosed fan assembly may include a rotor having an outer periphery andat least one slot extending radially inwardly through the outerperiphery of the rotor. The slot may terminate at a base surfacedisposed at a radial depth from the outer periphery of the rotor. Thefan assembly may further include at least one fan blade including anairfoil connected to a root. The root maybe received in the slot. Theroot may terminate at an inner face. The root has a radial length thatis less than the radial depth of the rotor slot to define a gap betweenthe inner face of the root and the base surface of the slot when theroot is biased away from the base surface of the slot. The fan assemblymay further include a spacer disposed in the gap. The spacer may befabricated from a polymer.

In another aspect, a method of coupling a fan blade to a rotor isdisclosed. The method may include providing a rotor that includes anouter periphery and at least one slot extending radially through theouter periphery before terminating at a base surface disposed at aradial depth from the outer periphery of the rotor. The method mayfurther include providing at least one fan blade including an airfoilconnected to a root. The root may terminate at an inner face and mayhave a radial length that is less than the radial depth of the slot. Themethod may further include providing a spacer fabricated from a polymer.The method may further include inserting the root of the fan blade intothe slot of the rotor and moving the root and fan blade radially awayfrom the base surface of the slot to expose a gap between the inner faceof the root and the base surface of the slot. The method may furtherinclude inserting the spacer into the gap.

In another aspect, a method of removing a fan blade from a rotor of afan assembly is disclosed. The method may include providing a fanassembly that includes a rotor including an outer periphery and at leastone slot extending radially through the outer periphery beforeterminating at a base surface disposed at a radial depth from the outerperiphery of the rotor. The fan assembly may further include at leastone fan blade including an airfoil connected to a root. The root maybereceived in the slot of the rotor. The root may terminate at an innerface and the root may have a radial length that is less than the radialdepth of the slot. The fan assembly may further include a spacerfabricated from a polymer and that is disposed between the base surfaceof the slot and the inner face of the root. The method may furtherinclude biasing the root radially outwardly away from the base surfaceof the slot, removing the spacer from between the inner face of the rootand the base surface of the slot and removing the root from the slot.

In any one or more of the embodiments described above, the polymer ofthe spacer may further include at least one reinforcing material.

In any one or more of the embodiments described above, the reinforcingmaterial may be selected from a group consisting of carbon fibers andglass fibers.

In any one or more of the embodiments described above, the spacer may beinjection-molded.

In any one or more of the embodiments described above, the polymer maybe selected from a group consisting of: polyetherimide (PEI), polyimide,polyether ether ketone (PEEK), polyether ketone ketone (PEKK),polysulfone, nylon, polyphenylsulfide, polyester, and combinationsthereof.

In any one or more of the embodiments described above, the slot may havea dovetail-shaped cross-sectional profile.

In any one or more of the embodiments described above, the base surfaceof the rotor slot is disposed between a pair of sidewalk that may extendfrom the base surface to the outer periphery of the rotor. The sidewalkmay extend towards each other to form a throat disposed between the basesurface and the outer periphery of the rotor. The base surface may havea width and the throat may also have a width. Further, the inner face ofthe root may be disposed between two pressure faces. The inner face ofthe root may have a width that is smaller than the width of the basesurface of the rotor slot and that is larger than the width of thethroat of the rotor slot.

In any one or more of the embodiments described above, the root of thefan blade and the slot of the rotor are shaped so that the root ismateably received in the slot.

Other advantages and features will be apparent from the followingdetailed description when read in conjunction with the attacheddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the disclosed methods andapparatuses, reference should be made to the embodiment illustrated ingreater detail on the accompanying drawings, wherein:

FIG. 1 is a sectional view of a gas turbine engine;

FIG. 2 is a perspective view of a rotor and fan blade that forms onepart of the fan assembly of the gas turbine engine illustrated in FIG.1.

FIG. 3 is a partial perspective view of the rotor and fan blade shown inFIG. 2 and with a disclosed spacer that maybe received in the gapbetween the root of the fan blade and the base surface of the slot ofthe rotor.

FIG. 4 is a perspective view of the spacer illustrated in FIG. 3.

FIG. 5 is another partial perspective view of the rotor and fan bladebut with the spacer disposed in the gap between the inner face of theroot of the fan blade and the base surface of the slot of the rotor.

FIG. 6 is an enlarged partial perspective view of the fan blade, rotorand spacer as illustrated in FIG. 5.

It should be understood that the drawings are not necessarily to scaleand that the disclosed embodiments are sometimes illustrateddiagrammatically and in partial views. In certain instances, detailswhich are not necessary for an understanding of the disclosed methodsand apparatuses or which render other details difficult to perceive mayhave been omitted. It should be understood, of course, that thisdisclosure is not limited to the particular embodiments illustratedherein.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

FIG. 1 is a sectional view of a gas turbine engine 10. The gas turbineengine 10 may include a fan section 11 that, in turn, may include a fanblade assembly 12. The fan blade assembly 12 may be mounted immediatelyaft of a nose cone 13 and immediately fore of a low pressure compressor(LPC) 14. The LPC 14 may be part of a compressor section 15 and may bedisposed between the fan blade assembly 12 and a high pressurecompressor (HPC) 16. The LPC 14 and HPC 16 may be disposed fire of acombustor 17, which may be disposed between the HPC 16 and a highpressure turbine (HPT) 18 that is part of a turbine section 19. The HPT18 is typically disposed between the combustor 17 and a low pressureturbine (LPT) 21. The LPT 21 may be disposed immediately fore of anozzle 22. The LPC 14 may be coupled to the LPT 21 via a shaft 23, whichmay extend through an annular shaft 24 that may couple the HPC 16 to theHPT 18. An engine case 25 may be disposed within an outer nacelle 26that surrounds the fan section 11.

Turning to FIG. 2, the fan blade assembly 12 may include a plurality offan blades 30 mounted to a rotor 31. More specifically, the rotor 31 mayinclude an outer periphery 32 through which a plurality of dovetailshaped slots 33 extend. The slots 33 may include inner base surfaces 34.The base surfaces 34 may each be disposed between inwardly slantedsidewalls 36, 37 that extend inwardly towards each other as they extendradially outwardly from their respective base surfaces 34. As also shownin FIG. 2, the slots 33 may each accommodate a correspondingly shapedroot 38 of a fan blade 30. The dovetail shaped root 38 may be connectedto a blade 39 that includes a leading edge 41 and a trailing edge 42.The leading and trailing edges 41, 42 are disposed on either side of theblade tip 43.

As shown in FIGS. 2-3 and 5-6, the root 38 may include an inner face 44that may be disposed between and connected to inwardly slanted pressurefaces 45, 46. The pressure faces 45, 46 may each engage the inwardlyslanted sidewalk 36, 37 respectively of their respective slot 33 in therotor 31.

While dovetail shaped slots 33 and roots 38 are shown herein, the readerwill note that other types of slots and roots, including but not limitedto fir tree shaped slots and correspondingly shaped roots are alsoclearly applicable to this disclosure and are considered within thespirit and scope of this disclosure.

Turning to FIG. 3, as described above, each slot 33 extends radiallyinwardly through the outer periphery 32 of the rotor 31. Each slot 33terminates at a base surface 34 that is disposed at a radial depth R₁from the outer periphery 32. The base surface 34 is disposed between andis connected to a pair of sidewalk 36, 37. The sidewall 36, 37 extendfrom the base surface 34 to the outer periphery 32 and extend towardseach other to form a throat at or below the outer periphery 32. Thethroat has a width W₁ as illustrated in FIG. 3. The width W₁ is lessthan the width W₂ of the base surface 34 as illustrated in FIG. 3. Inother words, the slot 33 may have a dovetail-shaped cross-sectionalprofile. As indicated above, other profiles, such as fir tree, T-shaped,etc. may be employed.

Turning to FIG. 5, the root 38 of the fan blade 30 also has adovetail-shaped cross-sectional profile. Specifically, the root 38extends radially inwardly before terminating at an inner face 44 thathas a radial distance R₂. The radial distance R₂ (FIG. 5) is less thanthe radial depth R₁ of each slot 33 (FIG. 3). Further, referring back toFIG. 5, the inner face 44 of the root 38 has a width W₃ that is lessthan the width W₁ of the throat of each slot. In other words, the root38 may have a complementary dovetail-shaped cross-sectional profile thatmatches the profile of the slots 33. Specifically, the inner face 44 ofthe root 38 is disposed between and connected to the pair of inwardlyslanted pressure faces 45, 46. When the fan blade 30 is biased in aradially outwardly direction, the pressure faces 45, 46 engage thethroat of the slot 33, which prevents the fan blade 30 from disengagingfrom rotor 31. Once the fan blade 30 is biased in a radially outwardlydirection, a gap 50 exists between the inner face 44 of the root 38 andthe base surface 34 of the slot 33 as illustrated in FIG. 3. To hold thefan blade 30 tight within the slot 33, a spacer 51 may be inserted intothe gap 50 as illustrated in FIGS. 5 and 6. The spacer 51, in additionto holding the blade 30 radially tight within the slot 33 may alsofacilitate balancing of the rotor 31 and may further prevent hammeringand/or relative motion between the pressure faces 45, 46 of the root 38and the side walls 36, 37 of the slot 33.

A perspective view of the spacer 51 is illustrated in FIG. 4. The spacer51 may have a thickness that is slightly less than or about equal to thethickness of the gap 50 illustrated in FIG, 3. Tapered side walls 52, 53surround the inner face 44 of the root 38 and enhance the ability ofspacer 51 to prevent hammering and relative motion of the fan blade 30within the slot 33. The upper surface 54 engages the inner face 44 ofthe root 38 while the bottom surface 55 engages the base surface 34 ofthe slot 33. Because the spacer 51 is fabricated from a polymericmaterial, it has a lower coefficient of friction than typical metallicmaterials used to fabricate such spacers and may be easier to insertinto the gap 50 than conventional metal spacers. Further, by using apolymeric material, weight savings and cost savings are also achieved.

An exemplary substrate for use in fabricating the spacer 51 is aninjection-molded, compression-molded, blow-molded, additivelymanufactured or a composite-layup piece formed of at least one of thefollowing: polyamide, polyetherimide (PEI), polyimide, polyether etherketone (PEEK), polyether ketone ketone (PEKK), polysulfone, nylon,polyphenylsulfide, polyester, or any of the foregoing with fiberreinforcement e.g., carbon fiber or glass-fiber.

Because the spacer 51 may be fabricated from a polymer, it may provide asubstantial reduction in cost versus a metallic spacer. For example,typical metallic spacers must be machined and, depending upon thespecific material used, can cost several hundred dollars. In contrast,an injection molded polymeric spacer may cost substantially less than ahundred dollars. The disclosed spacers 51 also are substantially lighterthan metallic spacers. For example, the composite materials listed abovehave a density of about ⅓ of the density of titanium and about ½ of thedensity of aluminum, which are both common metal spacer materials.

While only certain embodiments have been set forth, alternativeembodiments and various modifications will be apparent from the abovedescription to those skilled on the art. These and other alternativesare considered equivalents in within the spirit and scope of thisdisclosure.

What is claimed:
 1. A fan assembly comprising: a rotor having an outerperiphery and at least one slot extending radially inwardly through theouter periphery and terminating at a base surface disposed at a radialdepth from the outer periphery of the rotor; at least one fan bladeincluding an airfoil connected to a root, the root being received in theslot, the root terminating at an inner face and having a radial lengththat is less than the radial depth of the slot to define a gap betweenthe inner face of the root and the base surface of the slot; a spacerdisposed in the gap, the spacer being fabricated from a polymer.
 2. Thefan assembly of claim 1 wherein the polymer is embedded with at leastone reinforcing material.
 3. The fan assembly of claim 2 wherein thereinforcing material is selected from the group consisting of carbonfibers and glass fibers.
 4. The fan assembly of claim 1 wherein thespacer is injection-molded.
 5. The fan assembly of claim 1 wherein thepolymer is selected from the group consisting of: polyamide,polyetherimide (PEI), polyimide, polyether ether ketone (PEEK),polyether ketone ketone (PEKK), polysulfone, nylon, polyphenylsulfide,polyester, and combinations thereof.
 6. The fan assembly of claim 2wherein the polymer is selected from the group consisting of: polyamide,polyetherimide (PEI), polyimide, polyether ether ketone (PEEK),polyether ketone ketone (PEKK), polysulfone, nylon, polyphenylsulfide,polyester, and combinations thereof.
 7. The fan assembly of claim 1wherein the slot has a dovetail-shaped cross-sectional profile.
 8. Thefan assembly of claim 1 wherein the base surface is disposed between apair of sidewalls that extend from the base surface to the outerperiphery of the rotor, the sidewalls extending towards each other toform a throat disposed between the base surface and the outer peripheryof the rotor, the base surface having a width and the throat having awidth; and the inner face of the root being disposed between twopressure faces, the inner face having a width that is smaller than thewidth of the base surface and that is larger than the width of thethroat.
 9. The fan assembly of claim 1 wherein the root and slot areshaped so that the root is mateably received in the slot.
 10. A methodof coupling a fan blade to a rotor, the method comprising: providing arotor including an outer periphery and at least one slot extendingradially through the outer periphery before terminating at a basesurface disposed at a radial depth from the outer periphery; providingat least one fan blade including an airfoil connected to a root, theroot terminating at an inner face and having a radial length that isless than the radial depth of the slot; providing a spacer fabricatedfrom a polymer; inserting the root of the fan blade into the slot of therotor; moving the root radially outwardly away from the base surface ofthe slot to expose a gap between the inner face of the root and the basesurface of the slot; and inserting the spacer into the gap.
 11. Themethod of claim 10 wherein the polymer is embedded with at least onereinforcing material.
 12. The method of claim 11 wherein the reinforcingmaterial is selected from the group consisting of carbon fibers andglass fibers.
 13. The method of claim 10 wherein the spacer isinjection-molded.
 14. The method of claim 10 wherein the polymer isselected from the group consisting of: polyamide, polyetherimide (PEI),polyimide, polyether ether ketone (PEEK), polyether ketone ketone(PEKK), polysulfone, nylon, polyphenylsulfide, polyester, andcombinations thereof.
 15. The method of claim 11 wherein the polymer isselected from the group consisting of: polyamide, polyetherimide (PEI),polyimide, polyether ether ketone (PEEK), polyether ketone ketone(PEKK), polysulfone, nylon, polyphenylsulfide, polyester, andcombinations thereof.
 16. The method of claim 10 wherein the slot has adovetail-shaped cross-sectional profile.
 17. The method of claim 10wherein the base surface of the slot is disposed between a pair ofsidewalls that extend from the base surface to the outer periphery, thesidewalls extending towards each other to form a throat disposed betweenthe base surface and the outer periphery, the base surface having awidth and the throat having a width; wherein the inner face of the rootis disposed between two pressure faces, the inner face having a widththat is smaller than the width of the base surface and that is largerthan the width of the throat; the moving of the fan blade radiallyoutward away from the base surface further includes moving of the fanblade radially outward away from the base surface until the two pressurefaces of the root engage the throat of the slot.
 18. A fan assemblycomprising: a rotor having an outer periphery and at least one slotextending radially inwardly through the outer periphery and terminatingat a base surface disposed at a radial depth from the outer periphery ofthe rotor; at least one fan blade including an airfoil connected to aroot, the root being received in the slot, the root terminating at aninner face and having a radial length that is less than the radial depthof the slot to define a gap between the inner face of the root and thebase surface of the slot when the root is biased away from the basesurface of the slot; a spacer disposed in the gap, the spacer beingfabricated from a polymer selected from the group consisting of:polyamide, polyetherimide (PEI), polyimide, polyether ether ketone(PEEK), polyether ketone ketone (PEKK), polysulfone, nylon,polyphenylsulfide, polyester, and combinations thereof.
 19. The fanassembly of claim 18 wherein the polymer is embedded with at least onereinforcing material.
 20. The fan assembly of claim 19 wherein thereinforcing material is selected from the group consisting of carbonfibers and glass fibers.